ARM: pxa: Don't rely on public mmc header to include leds.h

Some of the pxa platforms, balloon3, colibri-pxa270-income, corgi,
trizeps4, vpac270, zeus and zylonite depends on leds.h. Explicitly include
it instead of relying on the public mmc header host.h.

Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: <linux-arm-kernel@lists.infradead.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>